Low Density Nanocellular Polymers Based on PMMA Produced by Gas Dissolution Foaming: Fabrication and Cellular Structure Characterization.

Judith Martín-De León,Victoria Bernardo,Miguel Rodríguez-Pérez

doi:10.3390/polym8070265

Abstract

This paper describes the processing conditions needed to produce low density nanocellular polymers based on polymethylmethacrylate (PMMA) with relative densities between 0.45 and 0.25, cell sizes between 200 and 250 nm and cell densities higher than 1014 cells/cm3. To produce these nanocellular polymers, the foaming parameters of the gas dissolution foaming technique using CO2 as blowing agent have been optimized. Taking into account previous works, the amount of CO2 uptake was maintained constant (31% by weight) for all the materials. Foaming parameters were modified between 40 °C and 110 °C for the foaming temperature and from 1 to 5 min for the foaming time. Foaming temperatures in the range of 80 to 100 °C and foaming times of 2 min allow for production of nanocellular polymers with relative densities as low as 0.25. Cellular structure has been studied in-depth to obtain the processing-cellular structure relationship. In addition, it has been proved that the glass transition temperature depends on the cellular structure. This effect is associated with a confinement of the polymer in the cell walls, and is one of the key reasons for the improved properties of nanocellular polymers.

Highlights

The research on cellular polymers is a popular topic in material science since the development of microcellular polymers in the 1980s at Massachusetts Institute of Technology (MIT) [1]
This has been reported by different authors for different systems such as poly (PET) [9], acrylonitrile butadiene styrene (ABS) [10], PVC [11] or PC [12]
Polymethylmethacrylate (PMMA) V 825T was kindly supplied by ALTUGLAS® International (Colombes, France) in the form of pellets

Summary

Introduction

The key reason that explains the interest in microcellular materials is that these materials improve the mechanical properties of conventional cellular polymers. This has been reported by different authors for different systems such as poly (ethylene terephthalate) (PET) [9], acrylonitrile butadiene styrene (ABS) [10], PVC [11] or PC [12]. These materials present better tensile and impact properties than conventional cellular polymers. To further improve the mechanical properties of these systems, there are two promising strategies: (1) improving the cellular structure by means of increasing the homogeneity of the cellular structure; and (2) reducing the average cell size [13,14]

Methods

Results

Conclusion